A fixing structure for fixing printed circuit boards is shown in FIG. 1. The fixing structure of a conventional multi-layer printed circuit board, shown in FIG. 1, includes a printed circuit board case 120 to which printed circuit boards 110 are fixed; the printed circuit boards 110 each having a through-hole 111 formed at each corner thereof; bolts 130 each having a protrusion portion 131; and nuts 132 with which the bolts 130 are fixed.
The fixing structure of the multi-layer printed circuit board, shown in FIG. 1, has a structure in which the protrusion portion of the bolt is inserted into the through-hole of the printed circuit board to fix the printed circuit boards to each other, and the printed circuit boards are fixed to the printed circuit board case by the nut.
When a plurality of printed circuit boards are connected using bolts each having a protrusion portion as shown in FIG. 1, there is a problem in that, as the number of connection means is increased, a connecting operation time is increased, and therefore, manufacturing cost is increased.
Further, there is a problem in that a component such as the bolt does not appropriately maintain a fixing force because the strength of the component is weak due to the continuous exhaustion such as vibration.
Meanwhile, the number of printed circuit boards used in a battery control device used in a electric automobile or hybrid automobile is large, and a large number of printed circuit board are mounted in a narrow space as automobiles tend to be miniaturized. Since it takes a long period of time to fix printed circuit boards with a low fixing force using the conventional method, there is a problem in that productivity is considerably lowered.